Hitherto, a heat-sensitive recording material which utilizes a coloring reaction of a colorless or pale-colored basic dye and a color developer and provides a color image by contacting both the coloring materials by the action of heat is well known.
Such a heat-sensitive recording material is generally not satisfactory in stability of recorded images, and the recorded images fade with a lapse of time. In particular, when it is preserved under a moistened condition or a fingerprint is deposited on the recorded image, the recorded image disappears within a relatively short period of time. Accordingly, its improvement has been strongly demanded.
In order to overcome these defects of the heat-sensitive recording material, the present inventor made extensive investigations especially on substances capable of improving the stability of the recorded image when used in combination with the basic dye and color developer.
As the result, the inventor found that when a compound represented by formula (I) or (II) as described later is used, a heat-sensitive recording material excellent in stability of recorded images can be obtained, and attained the present invention.